A fire protection system for an industrial oil cooker is shown and described in U.S. Pat. No. 7,789,165. The '165 patent provides an oil cooker that has a longitudinally elongated cooker pan, a longitudinally elongated hood directly above the pan; and mist producing nozzles that are piped and disposed beneath the top wall of the hood and above the pan of oil. To assure mist suppression of flames or combustion on the oil surface, the height of the hood above the oil is selected and moved to an appropriate height above the pan. The '165 patent describes a method and system of fire protection in which a mist stream is formed at each nozzle at a water pressure of between, 50 and 1,500 psi and preferably above 260 psi. To accomplish this protection scheme, the nozzles are spaced with a rectangular surface zone of oil below each nozzle, and centered above each zone such that the mist is propelled downward to diverge and impinge on the oil surface to cover the oil in its respective rectangular surface zone. The nozzles may be carried by the top wall of the hood so as to project through a surface of the top wall. The hood is provided with a hood vent that has a mist nozzle disposed on a vertically extending wall of the hood vent. The vent nozzle can be angulated by a provision to cause the mist to be propelled in a selected lateral or longitudinal direction. Although the system of fire protection of the '165 patent provides a fire protection approach for an industrial oil cooker at a range of operative pressures between 50 and 1500 psi, the system is shown and described as being applicable to hoods and exhaust vents of a particular configuration, e.g. being either vertical or horizontal with respect to the oil surface, and instructs that the hood should be moved in a vertical manner to ensure appropriate coverage of the oil surface by the nozzles instead of identifying a particular nozzle spray pattern to be utilized for the protection of an industrial oil cooker. Due to the failure of the '165 patent to specify an appropriate mist pattern for addressing a fire in the oil of an industrial oil cooker, the fire protection system of the '165 patent fails to address industrial oil cookers that have their hood surface in a fixed positions with respect to the oil surface, e.g., regardless if the hood surface is parallel to the oil surface or angled to the oil surface.
While various mist nozzles are known in the art that operate in the pressure ranges specified by the '165 patent; the inventors have discovered that the structural configuration of these nozzles is insufficient to provide a spray pattern that addresses the deficiency of the fire protection system of the '165 patent with a nozzle having a minimum operating pressure to be considered a low or medium pressure system. The structural details of known fire protection sprinkler nozzles are shown and described in each of U.S. Pat. Nos. 5,392,993; 5,505,383 and 5,829,684 and U.S. Patent Publication No. 20110315406. Each of these nozzles has a specific orifice and diffuser configuration, i.e. an orifice insert which defines the orifice that has an inlet diameter that is equal to or greater than the outlet diameter of the insert, and an axially aligned diffuser that is larger than the orifice. Thus, a mist nozzle configuration is needed that will allow for operation at commercially desirable pressures and with various hood configurations of industrial oil cookers.